The invention relates generally to reading identification badges, and more particularly to reading colored badges using a camera and a vision system.
Most prior art machine-readable badges, for example, bar codes and magnetic stripes, require some close proximity-between the badge and the badge reader, and can read only one badge at the time.
PCT Patent Application WO 00/04711 xe2x80x9cImage Identification and Delivery Systemxe2x80x9d with an international filing date of Jul. 13, 1999 describes a segmented tag for identifying individuals. There, a color photograph is converted to a gray-scale image upon which edge detection is performed. The system also converts from RGB to HSV colors and segmentation. The results of-the edge detection and color detection are ANDed to provide an indication of the identification tag. The system also checks the outer circumference of the tag, and the outer diameter of a central region.
That system has a number of deficiencies. First, the system only works with a single image. Second, the system requires that the individual wearing the badge is identified. Third, the camera needs to be aimed at the badge. Fourth, the camera needs to be activated either by the photographer, a system operator, or a radio signal. Fifth, the badge must be photographed face on. Sixth, the system does not process the image in real-time.
Therefore, it is desired to provide a machine readable badge, which can be read at a distance, and a system that can read multiple badges at the same time, and which can read badges from various angles. In addition, it is desired that the system operates passively in real-time without human intervention.
A method dynamically identifies a badge in a sequence of images of a scene acquired by a camera. Each image in the sequence includes a plurality of pixels, and each pixel has a color and an intensity. Each image is scanned to detect a border pixel. Adjacent pixels to the border pixel are connected to determine a connected region of pixels. An inner boundary of the connected region is determined, and an ellipse is fitted to the inner boundary. The internal pixels inside the ellipse are distorted to a circular form, and a plurality of spokes are fitted to the distorted internal pixels to identify colored segments. Then, an unique identity is associated with each badge according to the colored segments.
The border pixel having a border color and an intensity greater than a first threshold, and the adjacent pixels having the border color and an intensity greater than a second threshold, where the first threshold is greater than the second threshold. The pixels of each image are scanned in a left-to-right and top-to-bottom order. Pixels in the connected region are followed in a forward and left direction to detect the inner boundary.